The following processes for producing such initiators from 1,4-diisopropylbenzene are known.
In one process, 1,4-diisopropenylbenzene (CH2═(CH3)CC6H4C(CH3)═CH2) is prepared by dehydrogenation (U.S. Pat. No. 3,429,941) and then undergoes addition reaction with hydrogen chloride (O. Nuyken et al., Makromol. Chem., 186, 173 (1985)). In another process, 1,4-bis(1-hydroxy-1-methylethyl)benzene (1,4-HO(CH3)2CC6H4C(CH3)2OH) is prepared by air oxidation (for example, Japanese Unexamined Patent Application Publication No. 60-174737) and is then allowed to react with hydrogen chloride (V. S. C. Chang et al., Polymer Bulletin, 4, 513 (1981)).
The above-described processes require at least two-step operations. A process for producing target 1,4-dicumylchloride in a single-step operation by allowing 1,4-diisopropylbenzene (1,4-H(CH3)2CC6H4C(CH3)2H) to react with a chlorine gas under sunlight irradiation is disclosed (M. S. Kharashch et al., J. Am. Chem. Soc., 61, 2142 (1939)). A reaction induced by light irradiation has a problem with the control of regioselectivity in chlorination.
However, each of such conventional processes uses a hydrogen chloride gas or a chlorine gas functioning as a reagent for chlorination, thus leading to gas-liquid reaction when the processes are performed. Therefore, there are problems in which yield is significantly affected by reaction conditions, such as stirring efficiency, and a large excess of a chlorinating reagent is required based on stoichiometry. Furthermore, the reaction must be performed at ice temperature. Consequently, these processes are not industrially advantageous processes.
The present inventors found a process for simply producing dicumyl chloride or the like in high yield by allowing an alcohol compound, such as 1,4-bis(1-hydroxy-1-methylethyl)benzene 1,4-HO(CH3)2CC6H4C(CH3)2OH, to react with hydrochloric acid (Japanese Unexamined Patent Application Publication Nos. 8-291090 and 10-175892).
With respect to a process for producing 1,4-dicumyl chloride by chlorination of the benzylic positions in 1,4-diisopropylbenzene, a process in which sodium hypochlorite is allowed to react in the presence of a phase-transfer catalyst (BU4N(HSO4)) is disclosed (H. E. Fonouni et al., J. Am. Chem. Soc, 1983, 105, 7672). However, this process uses an expensive phase-transfer catalyst and thus is not an industrially advantageous. A process in which chlorination is performed with hypochlorous acid without a phase-transfer catalyst is also disclosed (F. Minisci et al., Chim. Ind., 70, 52 (1988). A process for producing 1,4-dicumyl chloride by chlorination of tertiary carbons in 1,4-diisopropylbenzene with hypochlorous acid has the advantages of being a single step and higher selectivity compared with photochlorination. However, hypochlorous acid is a significantly unstable substance; hence, it is difficult to constantly prepare hypochlorous acid of the same concentration and store the prepared hypochlorous acid. Therefore, when a specific amount of feed is set based on an amount of a material, the equivalent relation between them does not stay the same, thus resulting in difficulties in achieving stable yield, stable selectivity, and stable product quality.
A process for producing 1,4-dicumyl chloride with hypochlorous acid is also disclosed in Japanese Unexamined Patent Application Publication No. 9-143106 but does not solve the above-described problems. Thus, Japanese Unexamined Patent Application Publication No. 9-143106 does not provide a production process suitable for commercialization. Japanese Unexamined Patent Application Publication No. 2000-63303 also discloses a process for producing 1,4-dicumyl chloride with hypochlorous acid. A crystallization operation is necessary for achieving higher purity and is performed using a refrigerator with the high expense of electricity. This results in an inevitable reduction in yield.